Numerous processes exist in the prior art for either physically or chemically modifying starches. Typically the modification to the starch is conducted while the starch is dispersed in an aqueous slurry. An integral step in these starch modification processes is the separation of the treated or modified starch solids from the aqueous slurry and the water washing of the separated starch solids before these solids are dried. These separation and washing steps are necessary in order to remove undesired compounds from the desired modified starch solids. These undesirable compounds may be naturally-occuring materials such as the flavors which are present in cereal starches or may be added chemicals, reaction products or salts which remain with the modified starch solids as a result of a chemical modification process and/or a pH adjustment step. Chemical modification usually involves cross-linking with, for example, phosphorous oxychloride, epichlorohydrin, acrolein, di-epoxy reagents, and the like. While such modifications can benefit the paste character and texture of the starch, the cross-linking agents are subject to regulations which limit the level of these materials which may be contained in the starch product. A disadvantage which is present with the prior art separation and washing techniques is the loss of starch solids contained in the aqueous phase of the slurry and in the wash water. This loss constitutes an economic penalty both in terms of lost product and the cost of disposing of these solids.
An example of a process wherein physically modified starch solids are washed with water is disclosed in U.S. Pat. No. 4,477,480 to Seidel et al. According to this patent the off-taste/flavor present in cereal starch, such as corn starch, is removed by forming an aqueous, 40% by weight, starch slurry, raising the pH of the slurry to between about 10 and 12.5, filtering the slurry to separate the treated starch solids, washing the separated solids with water, and then drying the washed solids. Examples in which chemically-modified starch solids are filtered, washed and then dried are set forth in U.S. Pat. No., 4,562,086 to Smolka et al. where a 37.2% by weight starch slurry is etherified and cross-linked and 4,228,199 to Chiu et al. where a 44% by weight starch slurry is cross-linked.